Automatic test and ringing circuits



H; D. CURRIEIT'AND H. H. IDE. AUTOMATIC TEST AND SINGING CIRCUITS. APPLICATION FILED SEPT- 9. I920.

Reissuggl Jan. 31, 1922. 15,277.

.FYZIEHYEI'E Hz'ramflfurrier Harrgfifde HZTQ I EF UNITED STATES PATENT OFFICE. T

HIRAM D. CURRIER, OF CHICAGO, AND HARRY H. IDE, OF LA GRANGE, ILLIL'l'OIS, ASSIGNORS TO KELLOGG SWITOHBOARD 8t SUPPLY COI'w'IPANY, OF CHICAGO, ILLI- NOIS, A. CORPORATION OF ILLINOIS.

AUTOMATIC TEST AND BINGING CIRCUITS.

Specification of Reissuecl Letters Patent.

Reissued J 2111.31, 1922.

Original No. 1,311,156, dated July 29, 1919,- Serial No. 19,169, filed April 5, 1915. Application for reissue filed September 9, 1920.

To all whom it may concern.

Be it known that we, HIRAM D. CURRIER and HARRY H. Inn, citizen of the United States of America, residing in Chicago and La Grange, respectively, county of Cook, and State of Illinois, have invented certainnew and-useful Improvements in Automatic Test and Ringing Circuits, of which the following is a. specification.

Our invention relates to telephone eX- vhange systems in which link or cord circuits are employed and has to do moreparticularly with systems in which automatic ringing or signaling means and an automatic busy test is provided, and has for its object the provision of a novel and improved system of the above type. Hitherto in telephone systems employing automatic busy testing means, it has been customary to include either marginal or polarized relays. Such systems are found to be unreliable and objectionable in certain respects. For example, should a plurality ofcalling connertions be extended to av called line at the same time,thus connecting the testing relays oi the diiierent link circuits in multiple, it has been. found that the marginal relays will fail to operate satisfactorily, due to the low resistance path established by connecting a plurality of these relays in multiple, and the result is that a. plurality of calling connections are connected to theline of the called subscriber at the same time. To overcome these object-ions we have arranged the testing means inthe form of alVheatstone bridge, so that the action of the testing relayismadepositive and not marginal. The testing relay either receives its full strength of current or no current at all, and this testing condition is maintained no matter how may connections are extended to the called line at the same time. v

Referring now to the accompanying sheet of drawings, Figure 1 diagrammaticallyrepresents a circuit connection between a calling substation A and :1 called substation connected through the medium oi the link circuit C. Figure 2 shows diagrammatiallv the test circuit that is established at the tiine a connection is extended to the line. of the, called subscriber. This circuit will be hereinafter more fully described. The common battery substationsA and B- Serial No. 409,252.

terminate in the central office equipment in the line circuits L and L, respectively. The substation A may be of any desirable or suitable type, and, as shown,is of the wellknown Kellogg common battery type. The line circuit L comprises a line relay LR, cut-. oli relay CO, line signal S and the multiple jacks J'. The substation B and line circuit L are similar in all respects to substation A and line'circuit L, except that a plurality ofsubstations are connected to the line conductors terminating in the central exchan e, the stubs of which are shownat B, T3? and B The cord circuit C comprises an answering plug AP and a calling plug GP, the two plugs being connected by the heavily marked conductors shown and having the condensers K and K interposed. Associated with the answering end of the cord circuit is a double-wound answering tip supervisory relay AT and an answering sleeve super visory' relay AS, the two relays controlling the circuit of the answering supervisory lamp AL. At the calling end of the cord circuit C is a calling tip supervisory relay- CT, a listening control relay LC and a switching relay Sl V. The calling tip supervisory relay CT and listening controlrelay LC control the circuit of the calling supervisory lamp CL. A party-line ringing the key R1; is shown for connecting one of a plurality of'generators to the common generator lead; 2, and for controlling the circuit of the ring ing control relay RD. The ringing control relay RD controls the normalconnection eX-, tending between the answering plug AP and the calling plug GP, and also: controls thecircuit of the ringing interrupter relay RI. The ringing interrupter relay RI, through the medium of the interrupter I, operates to intermittently apply ringing current to the line of the called sub-; scriber. The operators set 0 is opera-.- tively connected to the strands of thecord circuit through the alternate contacts and 5 of the answering supervisoryrelay A S when connection is established to the line of a calling subscriber and is disconnected therefrom at normalcontacts 6. and 7 .ot'the listening control relay LC when connection is established to the line of the called sub 105 scriber. The testing relay TR associated,

cutoff relay GO to ground.

" relay AT.

with the calling end of the cord circuit determines Whether or. not a connection is to be extended? .to the line of the called subsoriber, that is, Whether ringing current is to be applied to-the line of the called subscriber or whether the busytone generator ET is to be connected to the line of the calling subscriber. We preferably arrange theresistances of the coils X and Y, of the sfitrre ay. and-of the cut-off relay 00, equal. The reason for this. will hereinafter appear. v

Having described in a general way the apparatus. embodying the preferred form of one-invention, we will now describe more in :detailitheoperation of the said apparatus iniestablishing a. connection between a calling "and a cal-led. substation.

.Assuming' now that the subscriber-at the substation A desires. a connection with the substation. B, the subscriber at substation A removing his receiver from the switchhook, closes an energizing circuit through the line relay LR, traced from battery through the winding of said line relay, normal contact 8 of the cut-off relay CO, to and through-the substation A, and through the normal contact 9 of relay CG to ground. The line relay LR, upon energizing, closes a circuit through the line lamp S, thus notifyingthe operator that the subscriber at substation A desires to make a call; The operator upon noting the glowing of line lamp S inserts the answering plug AP of the cord circuit G into jack J of the callingsub s'cribers line equipment. The insertion of the answering plug AP into the jack J closes a series energizing circuit through the cutoff relay GO and the answering sleeve supervisory' relay AS, traced from battery through the winding of said answering sleeve supervisory relay AS, sleeve contact of t-he p'lug AP-andjack J and through the The cut-off relay GO, uponenergming, disconnects the line relay LR from the line of the calling subscriber; The answering sleeve supervisory relay AS, upon energizing, connects operators set 0 through its alternate con tacts t and 5 to the cord circuit C. A further result due to the insertion of the plug into the jack J, is the closing of a circuit throu h answering tip supervisory he answering tip supervisory relay AT, upon energizing, prevents a premature glowing of the answering supervisory lamp AL by opening of its contact 10. The operator now inquires the wants of the calling subscriber, and assuming that it is the subscriber B that is wanted, the operator, without testing, inserts the calling plug OP into the jack J connected to the line of the called subscriber B. Upon the insertion of the calling plug GP into .the jack J, a circuit is closed through the test control refurther result due to the energization of test controlrelay TGR is the closing of a circuit through the listening control, relay LC, traced from battery through the winding of the said relay LC and through alternate contact 17 of test control relay TGR to ground. The listening control relay LG, upon energizing, disconnects the operators set 0 from the cord circuit C at its normal contacts 6 and 7. The operation of the apparatus so far occurs whether the called line is in an idle or busy condition.

Assuming the called Zine The test control relay TOR, upon energizing, also closes a circuit through thetest relay TR, traced from battery through the resistance Y, the winding of the test relay TR, alternate contact 13 of ,relay TOR, sleeve conductor of the plug GP and 'ack J and the winding of cut-off relay 0 to ground. It will be noted that ground is connected through alternate contact 12 of answering sleeve supervisory relay AS, through the resistance X, normal contact 15 of test relay TR to a point intermediate one terminal of the test relay TR and one terminal of the resistance Y. That is, one terminal of the test relay TB is connected through equal resistance Y and X to bat tery and to ground. Referring to Fig. 2, it will be noted that the resistances X and Y form two arms of the Wheatstone bridge, while the resistance of the cutoff relay CO forms a third arm of the Wheatstone bridge, the fourth arm Z being open (when a line is idle). When the test relay TB is bridged from point 14: to point 13 of the Wheatstone bridge the test control relay TCR is energized. Owing to the unbalanced condition of the lVheatstone bridge (since the fourth arm is opened) the test relay TR receives sufficient current over the above traced circuit to operatively energize. The test relay TR, upon energizing, closes a locking circuit for itself, extending from battery through its alternate contact 16, winding of said test relay TR, contact 13 of test control relay TGR, sleeve contacts of calling plug GP and jack J and winding of cut-ofi relay CO to ground. The cut-off relay CO, upon energizing, disconnects the line relay LR from the line of the called subscriber B.

' SW and disconnects the resistance The test relay TR, upon energizing, also closes a circuit through the switchin relay from point 14 of the VVheatstone bridge, shortcircuits the resistance Y and places itself between battery and point 13 (as shown dotted in Fig. 2). That is, the resistances X and Y are disconnected and the cut-off relay CO and test relay TR are connected to form two arms of the Wheatstone bridge to establish a busy condition, as will be hereinafter fully described. The switching relay SW, upon energizing, prevents the applying of the busy tone from busy tone generator BT to the line of the calling subscriber and connects the tip and ring conductors of the calling plug GP to the strands of the cord circuit. The operator now depresses one of the ringing key plungers to connect one of the ringing generators to the common ringing conductor 2 and to close a circuit for ringing control relay RD through its end contact 3. The operator upon removing pressure from the plunger of the ringing key RK, allows the end contacts 3 to return to normal, but connection is maintained be tween the selected ringing generator and the common ringing lead 2. The circuit for ringing control relay RD extends from battery through the winding of said relay, through end contact 3 of ringing contact RK, alternate contact 18 of listening control relay LG, normal contact 19 of calling tip supervisory relay'CT to ground. Ringing control relay RD, upon energizing, closes a locking circuit for itself extending from battery through its winding, through its alternate contact 20, alternate contact 18 of listening control relay LC and normal contact 19 of calling tip supervisory relay CT to ground, and also closes a circuit through the ringing interrupter relay RI, traced from battery through the interrupter I, through winding of said interrupter relay RI and through alternate contact'21 of relay RD to ground. The ringing interrupter relay RI operates to intermittently apply rin ing current from the common ringing lead 2 to the line of the called subscriber through the medium of the interrupter I. Upon the response of the called subscriber a circuit is closed through the calling tip supervisory relay CT extending from battery through lower winding of said relay, alternate contact 6 of the listening control relay LC, normal contact 22 of the relay RI, alternate contact 23 of relay SW, ring conductor of the calling plug GP and jack J, toand through the substation B. tip conductor of jack J and calling plug GP, alternate contact 2 1 of relay Sl/V, normal. contact 25 of relay RI, alternate contact 7 of relay LC and through the upper winding of the said. calling tip supervisory relay CT to ground. The calling tip supervlsory relay,

upon energizing, opens the circuit of the calling supervisory lamp CL at its contact 26 and opens the circuit of the ringing control relay RD at its contact 19. The ringing control relay RD, upon cle-energizing, opens the circuit of the ringing interrupter relay RI at its contact 21 and closesconnection between the calling and called end of the cord circuit C. The subscribers may now carry on conversation over the heavily marked conductors. 7

Assuming now that the subscribers have completed their conversation, the calling subscriber A, upon replacing his receiver, opens the circuit of answering tip supervisory relay AT at the switchhook contacts. The answering tip supervisory relay AT, upon re-energizing, closes a circuit through the answering supervisory lamp AL at its contact 10. The called subscriber upon' replacing his receiver open the circuit of calling tip supervisory relay CT at the switchhook contacts at the substation, allowing the said relay CT to de-energize. Relay CT upon de-engerizing, closes a circuit through the calling supervisory lamp CL at its contact 26. The operator, upon noting the answering supervisory lam AL and the calling supervisory lamp (1L glowing, removes answering plugAP and callingplug UP from their respective jacks J and J, allowing the apparatus of the cord circuit C and cut-01f relays CO and C0 of the calling and called line circuits L and L to return to normal.

Called Zine busy.

If the line of the called subscriber is busy, the winding of the test relay TR of the connected link circuit and the winding of the cut-off relay CO will be connected to point 13 of the Wheatstone bridge, as shown in Fig. 2, and as hereinbefore described. Now, upon insertion of the calling plug OP of the calling link circuit into jack J of the called subscriber, the test control relay TC'R will energize (the same as heretofore described), but the test relay TR will fail to receive current, as it is bridged across points 13, 14: of the VVheatstone bridge and since the arms of the bridge are now in balance. The relay TR failing to energize, fails to close a circuit through switching relay SW. Since switching relay SW does not energize, the tip and ring conductors of the calling plug CP are not connected to the strands of the cord circuit C, but the busy tone from the busy generator BT will be applied to the line of the calling subscriber A. This circuit may be traced 125 from battery through the busy tone generator BT, alternate contact 28 ofrelay TCR, normal contact 29 of relay SW, through the condenser K to and through calling substation A and back through the upper wind- 130 nngerof theringingwkey. BK to initiate.

the operation of; the. automatic ringing apparatus,current Will not reach'the line of the called subscribeniasthe tip and ring-com ductors oi-wthe plug GP are disconnected from, the strands. v3.01am. 31 of the cord circuit C. at contactsfil: and123 of the switching relay ;'%Ih.e calling subscriber upon receiving the busy signal replaces. hisreceitver upon the switchhook and opens the circuit of answering tip supervisory .relay AT. The answering tipsupervisory relay. AT, uponde-energizi11g,.closesa circuit for answering snpervisory lamp AL. The operator noting the glowing of: lamps AL and CL, removes pl'ugsAP and'GP from their respective jacks.

Assumingnowthat a plurality of connections are-extended to the line of the-called subscriber by way of the multiple jacks J,

itis to be noted that the balance of the.

lVheatstone bridge is unaffected, and that the test relay TR. and the resistances X and Y will be connected in in the manner shown in-Fig. 2, thus always maintaining the balance of the brid e and preventing any cur rent whatever rom flowing through the- :windings of the test relays TR of the calling line circuits.

While we have illustrated a preferred embodiment .of our invention, it is apparent that it may be applied in various ways, and also that many modifications and changes will readily suggest themselves to those skilled in the art. Therefore, we do not desire to be limited to the exact structure as shown, but aim to cover all that which comes within the spirit and scope of: the appended claims;

Having described our invention, what We claim as new and desire to secure by United States Letters Patent, is:

1. Atelephone system including-a manual link circuit having a calling terminal, a called telephone line, manual means for connecting the calling terminal of said link circuit-to said called telephone line, a test relay for testing the busy or idle condition of'said called line, said test relay being normally disconnected from said calling terminal, arelay 'for connecting said test relay 'to said calling terminal whereby said test relay is supplied with current and operatively energized if said line is idle, and is deprived of all current it said line is busy.

' 2. A telephone system comprising a link circuit having a calling terminal, a called telephone line, manual means for connecting said calling terminal thereto, a test relay for said link circuit, means for supplying current to said test relay if said line is idle,

means for preventing the flow of current through the said relay if the line is busy,

and 'a second-relay dependent upon: the=op;eration "021:: the 'saidctest "relay for. operatively connecting: the said link circuit to the saidcalled -line..

3. A telephone system comprising a link circuit provided :with a plug terminal, a calledtelephone line vand means. for connect? ing said plug terminal to said line, a test relay for testing the busy; or idle condition of saidcalled .line, means- :for supplying Y curs rent to said. test relay if. said line' is idle, means for. preventing the flow of: current through theisaid relay-if; the-line is busy, and: assecondi relay -dependent.=upon the operation of the saidltest relay fer;- connectingalousy signal to the answering end of the said. link circuitv 4. A-telephone system including, a manual link circuit having athrees conductor calling terminal, a carlled isubseriberls' line, manual means ion 1 connecting the, said. terminal to thesai'd calledqline, a test relay normally disconnected tronrsaid calling terminal, a

relayfor connecting said test relay to said calling terminalwhereby said; test relay. receives suflicient currentto operatively energize if the called line is idle, but is entirely deprivedof current if the called- .line isbusy, and-means controlledby'saiel test relay upon energization to operatively associate said link circuitwith the said called line.

5, A- telephone system including a link circuit having "a three-conductor calling terminal therefor, a called subscribers line, manual means for connecting the said terminal to the called Line atestin g, relay normally disconnected.tromysaid terminal, saidtest relay being, adapted to determine the operative connection between said link circuit' and said line, asecond relay for connecting said test relay tosaid terminal whereby said test relay then receives current sullicient for it to operatively energize if the called line tests idle, but is entirely prevented from receiving any current whatsoever it the called line tests busy.

6. The combination of a called subscribers line and anthree-conductor manually controllediteianinal for connection with said line, attest relay connected to a conductor o tE sztidterminahaneans for closing a. circuit through the said test relay if the called line tests idle, means for preventing. a flow of current throughthe said test relay it the called. line tests busy, and a relay con trolled by said test relay for operatively connecting the said. link circuit to the subscribers line.

7. The combination of a called subscribers line and a link circuit provided With a threeconductor terminal for connection with said line, a test relay connectecl'to a conductor of said terminal, means dependent upon the condition of said called line for either closing a circuit through the said relay if the line tests idle or for preventing a flow-of current through the said relay if the vlinc tests busy, and an electromagnct controllable by said testing relay for operatively connecting the said link circuit tothe subscribefs inc. 1 z 8. A telephone system comprisinga-l-ink circuit having a terminal therefor, a called subscribers line circuit andmeans for con uecting the said. terminal thereto, testing means associated With-the said link-circuit comprising a test relay and various resistances adapted to-be connected in the form of a lVheatstone bridge for testing the'busy or idle condition of the said called line.

'9. A telephone system comprising; a link circuit having a terminal,- :a called subscribers line circuit having a: cut-off ,relay associated therewith, means for connecting thesaid' terminal with the line circuit, a test relay and a plurality of resistance coils for said link circuit, means for connecting the said resistance coils and the said cut-off relay to form arms for a Vl heatstone bridge, means for connecting the said test relay across opposite points of the said bridge, and means dependent upon the condition .of said called line for either supplying or preventing the How of current through the said test relay.

10. A telephone system including a called subscribers line, a manually controlled link circuit adapted to be connected to said line, a test relay for said link circuit for testing the busy or idle condition of said called line, and a second relay for connecting said test relay to a terminal of said line whereby said test relay receives current to operatively energize if said line is idle, or is prevented from receiving any current whatsoever if said line is busy and remains in its normal position.

11. A telephone system including subscribers telephone lines, a link circuit provided with a air of terminals for interconnecting said lines, a test relay for said link circuit, means for either supplying or depriving said relay of current when. connected to a called one of said lines according to whether said line is in an idle or a busy coudition, and a relay controlled by said test relay for operatively connecting the said link circuit to the subscribers line.

12. A telephone system including a called subscribers line, a manually controlled link circuit provided with testing apparatus, said apparatus including a test relay havlng one of its terminals connected to both poles of a battery, means for connecting sald apparatus to said telephone line whereby sa1d apparatus is deprived or recelvescurrent according to the busy or idle condition of the called telephone line. i I

13. A telephone system including a called 65 subscribers telephone line, a manual llnk circuitv provided with a testing device, a ringing current-generator anda busy signalingidevice associated With saidv link circuit, means for associating =said testing device with-said subscribers line whereby-said test device J'eceives"operating CuITenl'ntO' connect said ringin currentgenerator to said line it said line is idle or said relay is entirely deprivedo-tcurrent and said busy signaling device:is-ope-ratively connected to a calling subscribers-lineif saidcalled line is busy;

lt A-telephone system including a-subscriber s telephone line provided with multi ple terminals, manual linkcircuits for con nection to-said line-through said terminals, testing apparatus .ror each of said link circuitsnorrnally disconnected from the termi nals-flot said-link-circuits, said -testing apparatus being. so arranged; that when I said line is tested asa busy linesaidapparatus-is entirely deprived of current no matter how many link circuits are connected to the line at the time said last link circuit is connected thereto.

15. A telephone system including a busy subscribers telephone line, a manual link circuit provided with a calling terminal, a

- test relay for said link circuit normally disconnected from said terminal, a second relay, operator-controlled means for connect- .ing said link circuit to said line, thereby operating the said second relay to connect said test relay to said busy line whereby said test relay is deprived of current due to the busy condition of the subscribers line, and an audible busy signaladapted to be trans- V mitted to the other end of said link circuit by said second relay.

16. A telephone system including a called subscribers line, a battery, a manually controlled link circuit provided with a test relay having its one terminal connected through resistances to the opposite poles of said battery, means for connecting said link circuit and testing relay to said telephone line whereby said relay will be deprived of or will receive current, according to the busy or idle condition of said called telephone line.

1?. A telephone system including a link circuit provided with a terminal, a subscribers line provided with a terminal for receiving said link circuit terminal, testing means for said link circuit including a test relay and various resistances adapted to be connected in the form of a Vlheatstone bridge for testing said line.

18. A telephone system includ ng a subscribers telephone line, a link circuit provided with a test relay connected to the op- 12 posite poles of a battery, a test contact for said telephone line adapted to be connected to one pole of said battery or to the opposite poles of said battery, means for connect ng said link circuit to said telephone hue whereby if-eaid: test eentadt is connected to on ly 'on'e polie' 'ef saidbabteny,- said -nest nelay will l'be enen ized tooperaeivelqy cenneet said battery said test relay will be deprived of ope-rating current and will *fail t'o: ener- A'tyelephone system including 'wsub- 'sorib'efs telephone line provided Wibhsmulti ple'berminals, aplurality of link circuitsfor connection? to said line-through its: saidmulti pl'e t-emninals, another link GlIGlllt pr0- vided with a testing relay also adapbed- 'it'o be connected lio said line through'one of its multiple terminals, said teslzing melay being so connected that when said line: :is- *te'sted as a busy line it is l deprived? of' current no matter how" many of said first-dink eitcuiis mwy'be-oonneoted to said- 120; A "telephone exohamge vsyetem includ- Gook and September, 1920.

mew

ling telephone li n'es"exlsejnding from substaiuons'fio a=mu1fiple switchboard, a telephone :set'foreach operatofls position the eat, 1ink connectors fer connecting said-substations,

means for conneetingsaid' set to a calling line by Way of one of said link connectors, automatiomeans to prevent a telephonic connection betweena calling line and a busy line whenone'of said link conneotors is conineeted to s 'a1d'busy line, means for disconineobmg sand set from said link connector when suclr connection is made and for sounding an audible signal in the telephone receiver at ehe calling substation, denoting said'bnsy condition of the called for line.

SignQd bg us at Ohicagq-in the county of tateof Illinois, this ith day of n. GURRIER. HARRY LD'E. 

